Autosomal recessive polycystic kidney disease (ARPKD; MIM 263200) is a relatively rare disorder, occurring in approximately 1 in 20,000 live births. Therefore, no single Center has sufficient patients for adequately powered clinical studies, genetic investigations, and/or therapeutic trials. Building on the established North American ARPKD Database and our extensive experience with mutational analysis of recessive PKD genes, including PKHD1, the objective of this Core: the ARPKD Clinical and Genetic Resource is to develop a unique set of clinical, genetic, and educational resources for ARPKD. This objective will be implemented in three specific aims. AIM 1 - Leverage the established North American ARPKD Database to build a comprehensive Clinical Database that includes all patients who meet the inclusion criteria for ARPKD. AIM 2 - Genotype children with classic ARPKD, as well as unusual recessive PKD phenotypes, for mutations in PKHD1 and/or the human orthologues of mouse recessive PKD genes and develop a Mutational Database. This Database will be capable of linking clinical and mutational information in a searchable format to facilitate genetic analyses (e.g. genotype-phenotype correlations, modifier gene studies), translational studies, and clinical trials. AIM 3 - Create a multi-media, web-based resource called "Understanding ARPKD". This Aim will address the paucity of reliable sources of information currently available to ARPKD families, their physicians, and genetic counselors. The distinctive feature of this Core is that it builds on clinical, genotyping, and educational programs already in place at UAB. Through the P30 mechanism, this Core will make these important resources available to the broader community of interested investigators, ARPKD families, and physicians/healthcare providers.